1. Field of the Invention
The present invention relates generally to improving sensors, more particularly to improving Fiber Bragg Grating (FBG) sensors and most specifically to improving the interrogation refresh rate of fiber bragg grating sensors.
2. Description of the Related Art
FBG sensors, which are basically gratings along optical fibers that act as mirrors to light sources, provide many attractive characteristics compared to other sensing systems. These include their inherent light weight, small size, and immunity to electromagnetic, radiation, and radio-frequency interference.
These features enable using many sensors on a single optical fiber at either interval or arbitrary spacing. Thus, a user can interrogate each sensor independently and obtain a distributed measurement over large structures. Because the gratings are multiplexed on a single fiber, many sensors can be accessed with a single connection to the optical source and detector. Conventional electronic strain gauge sensors require each sensor to have its lead wires attached and routed to the sensor readout. Therefore, for many types of large structures or remote sensing, FBG sensors provide a significant improvement over electronic strain gauge sensors.
Due to the above, FBG sensors are highly attractive to the aerospace community. For example, U.S. Pat. No. 5,798,521 discloses an apparatus and method for measuring strain in structures using a plurality of FBG sensors and an improvement to this apparatus and method is disclosed in U.S. Pat. No. 6,566,648. These patents are hereby incorporated by reference into this application. While the systems described in these patents do provide certain advantages to electronic strain gauge systems, one major disadvantage relates to the interrogation refresh rate. The maximum interrogation refresh rate employing the system described in U.S. Pat. Nos. 5,798,521 and 6,566,648 has been improved to approximately 1 scan per second. However, the desired refresh rate for strain sensor systems for the aerospace community is about a minimum of 10 scans per second.
Therefore, it is desired to provide an Optical Frequency Domain Reflectometry (OFDR) FBG sensor system that increases the refresh rate so OFDR FBG sensor systems may be employed by the aerospace community and other industrial communities requiring increased sensor refresh rates.